Macromolecular drug complexes and compositions containing the same

ABSTRACT

Macromolecular drug complexes containing a drug, like human growth hormone, and a polymer having a plurality of acid moieties, like carboxyl moieties or phosphonic acid moieties, and compositions containing the same, are disclosed. Compositions, particularly microemulsions, containing the macromolecular complexes are administered to individuals suffering from a disease or condition, and the complexes release the drug, in vivo, to treat the disease or condition, and to reduce, eliminate, or reverse complications associated with the disease.

FIELD OF THE INVENTION

The present invention relates to macromolecular drug complexes and to the administration of compositions containing the macromolecular drug complexes to individuals. More particularly, the present invention relates to a drug delivery system comprising a macromolecular drug complex containing a therapeutic agent that is noncovalently bound, i.e., is complexed, to a polymer having a plurality of acid moieties. The macromolecular drug complex is incorporated into a microemulsion to provide the drug delivery system. The complex is prepared by interacting the polymer and a therapeutic agent, such as human growth hormone, in an aqueous medium. Depending on the physicochemical properties of the polymer and therapeutic agent, the resulting macromolecular drug complex either is water soluble or separates from the aqueous medium as a solid precipitate. The macromolecular complex is incorporated into a microemulsion for administration of the therapeutic agent.

BACKGROUND OF THE INVENTION

It is well known that modern day drugs are very efficacious with respect to treating acute and chronic diseases. However, several diseases, and especially chronic diseases, are associated with complications that are not treated by administration of the drug.

For example, the standard treatment for diabetes is administration of insulin. An individual suffering from diabetes does not produce sufficient insulin, and hence the individual cannot burn and store glucose. Diabetes cannot be cured, but diabetes can be treated by periodic injections of insulin. FIG. 1 shows that serum insulin levels rise from a low fasting value to a peak after about 30 to 60 minutes, then fall back to a low value after about 120 minutes. In mild diabetics, the rise in serum insulin is lower compared to normal individuals. In severe diabetics, no insulin is produced, and the rise in serum insulin levels is negligible. As a result, excess glucose accumulates in the blood of a diabetic, which can result, for example, in a loss of weight and loss of strength.

However, insulin injections to treat diabetes do not treat, or alleviate, the serious vascular complications associated with diabetes, including nephropathy, retinopathy, neuropathy, heart disease, and reduced blood circulation in the limbs, i.e., “diabetic foot,” that can lead to gangrene. Another disadvantage with respect to the present therapeutic compositions used to treat diabetes is that insulin must be injected. Insulin cannot be administered orally because insulin is destroyed by the strong acid conditions of the stomach.

Therefore, it would be advantageous to develop a method of both treating a disease, and preventing or reversing complications associated with the disease. It also would be advantageous to develop easier methods of administering a drug to treat the disease. As set forth in detail hereafter, the present invention is directed to macromolecular drug complexes, to compositions containing the complexes, and to use of the complexes to reduce, eliminate, or reverse complications associated with a disease. The present invention is further directed to improved drug delivery systems for administering difficult to administer drugs, like insulin and human growth hormone.

With respect to diabetes, glycosaminoglycans (GAGs) are a class of negatively charged, endogenous polysaccharides composed of repeating sugar residues (uranic acids and hexosamines). GAGs have been shown to bind a variety of biological macromolecules, including connective tissue macromolecules, plasma proteins, lysosomal enzymes, and lipoproteins. In addition, exogenous GAGs have been shown to bind to the cell surfaces of a variety of different cell types, including liver cells (hepatocytes), fibroblasts, and importantly, endothelial cells. Exogenous GAGs, therefore, can be internalized. Furthermore, GAGs have been implicated in the regulation of cell proliferation and in cell-cell communication, shown to interact with cell-surface receptors (cell adhesion molecules), and shown to modify the behavior of cells in culture. In addition, GAGs were shown to be highly potent, selective inhibitors of HIV replication and giant cell formation.

GAG-receptor interactions are characterized by the formation of noncovalent, self-assembling macromolecular complexes. These transient, interpolyelectrolyte complexes mediate many biological functions including enzyme-substrate binding, antigen-antibody interactions, leukocyte-endothelial cell adhesion events, drug-receptor binding, and protein-protein interactions. Furthermore, secondary binding forces, such as hydrogen bonds, van der Waals forces, and hydrophobic interactions, govern interpolyelectrolyte formation, and, ultimately, influence the resulting pharmacologic response to the complex.

G. Gambaro et al., Kidney Int., 46, pages 797-806 (1994) discloses that exogenously administered GAGs have a favorable effect on morphological and functional renal abnormalities in diabetic rats, and appear to revert established diabetic renal lesions. Furthermore, D. M. Templeton, Lab. Invest., 61(2), pages 202-211 (1989) and C. W. Marano et al., Invest. Ophthalmology Vis. Sci., 33(9), pages 2619-2625 (1992) disclose that diabetic patients have a decreased glycosaminoglycan content in glomerular basement membranes. Additionally, an increase in total GAG serum levels in diabetic patients was disclosed in K. Olczyk et al., Acta Biochimica Polonica, 39, pages 101-105 (1992). The authors observed an increase in protein-bound GAGs, such as keratan sulfate, hyaluronic acid, heparin sulfate, and heparin in diabetic patients. Gambaro et al. also discloses an increase in the urinary excretion rate of GAGs from insulin-dependent diabetic patients.

Therefore, publications show that glycosaminoglycans play an important, yet unexplained, role in the vascular changes associated with life-long insulin therapy. In particular, administration of GAGs to diabetic animals has inhibited or reversed some vascular abnormalities. The publications also strongly suggest that exogenous insulin plays a role in elevating the level of GAGs in the urine and serum of diabetic patients. Furthermore, the publications clearly show that glycosaminoglycans bind to a multitude of biological macromolecules, including proteins.

These observations appear to suggest utilizing glycosaminoglycans as an adjuvant to insulin therapy. However, GAGs are anticoagulants and long term use of GAGs with insulin may thin the blood of an individual. The risks associated with a long-term use of GAGs also are unknown. Although GAGs have been used as therapeutic agents, e.g., heparin, GAGs have not been used for extended periods of time, or for the treatment of a chronic disease or condition, like diabetes. The present invention is directed to drug complexes and compositions containing the drug complexes, that provide the benefits of a drug GAGs complex, but that avoid the disadvantages associated with long term administration of a GAG compound.

Similar to endogenous GAGs complexes discussed above, GAGs and other naturally occurring and synthetic anionic polymers have been complexed with various therapeutic agents to provide a macromolecular drug complex, which then is incorporated into a microemulsion for administration to an individual, e.g., by oral or parenteral delivery, for example. The present drug delivery system makes it possible to regulate the pharmacologic response, and the route of administration of many drugs, by a judicious selection of polymer ionically complexed to the drug.

SUMMARY OF THE INVENTION

The present invention is directed to a drug delivery system comprising a drug complexed with a polymer having a plurality of acid moieties. The macromolecular drug complex is incorporated into a microemulsion to provide a drug delivery composition of the present invention.

The macromolecular drug complexes treat the underlying disease or condition, e.g., insulin to treat diabetes or human growth hormone to treat dwarfism, hypopituitarism, hypercholesterolemia, hypertension, depression, muscle wasting, osteoporosis, insomnia, menopause, impotence, as well as other conditions commonly associated with aging, and complications associated with the disease or condition, e.g., prevent or reverse the vascular problems associated with diabetes. The present macromolecular drug complexes can be water soluble or water insoluble at neutral pH. Therefore, the macromolecular drug complex can be administered in a variety of dosage forms.

More particularly, the present invention is directed to a drug delivery composition comprising a microemulsion incorporating a macromolecular drug complex. The macromolecular drug complex contains a drug and a polymer having a plurality of acid moieties and a weight average molecular weight (M_(w)) of about 1,000 to about 50,000. In accordance with an important aspect of the present invention, the drug contains at least one quaternary ammonium nitrogen atom for binding to, and complexing with, the polymer. Preferred drugs are polypeptides or proteins. The polymer contains a plurality of acid moieties for complexing with the drug. The acid moiety can be a carboxyl group, sulfate group, sulfonate group, phosphonic acid group, phosphoric acid group, phenolic group, or a similar acid moiety.

Another aspect of the present invention is to provide a macromolecular drug complex wherein the polymer is a naturally occurring polymer or a synthetic polymer.

Another aspect of the present invention is to provide a macromolecular drug complex containing a drug and a polymer in a weight ratio of drug to polymer of about 10 to about 90 to about 90 to about 10.

Yet another aspect of the present invention is to incorporate the macromolecular drug complex into a microemulsion, wherein the drug complex can be administered to an individual in a liquid form.

Another aspect of the present invention is to provide a microemulsion composition comprising a macromolecular drug complex that can be administered to an individual to treat an acute or chronic disease or condition, and to alleviate, eliminate, or reverse complications associated with the disease.

Another aspect of the present invention is to provide a microemulsion composition comprising a macromolecular drug complex remains intact and does not dissociate immediately after administration, and that are capable of releasing the drug in vivo to treat a disease.

Still another aspect of the present invention is to provide a composition containing a macromolecular drug complex wherein the drug is human growth hormone, insulin, methotrexate, isoniazid, chloroquine phosphate, a polypeptide, or a protein.

Another aspect of the present invention is to provide a microemulsion containing a macromolecular drug complex containing human growth hormone and a naturally occurring polymer, like heparin.

Yet another aspect of the present invention is to provide a microemulsion comprising a macromolecular growth hormone complex that treats dwarfism, hypopituitarism, hypercholesterolemia, hypertension, depression, muscle wasting, osteoporosis, insomnia, menopause, impotence, as well as other conditions commonly associated with aging.

One other aspect of the present invention is to provide alternate routes of administration for the safe, easy, and effective delivery of a therapeutic agent, especially to provide an oral route of administration for insulin, human growth hormone, and other drugs.

These and other novel features and aspects of the present invention will become apparent from the following detailed description of the preferred embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plot showing insulin levels (μU/mL) over time (minutes) for normal individuals and diabetics;

FIG. 2 are plots of turbidity (NTU) vs. weight % polymer in the complex for mixtures of 1.0 mg/mL insulin solution with various amounts of polyvinylphosphonic acid, both for polymer added to the insulin and for insulin added to the polymer;

FIG. 3 are plots of turbidity (NTU) vs. weight % polymer in the complex for mixtures of 1.0 mg/mL polyvinylphosphonic acid with various amounts of insulin, both for polymer added to the insulin, and for insulin added to the polymer;

FIG. 4 are plots of turbidity (NTU) vs. weight % polymer in the complex summarizing and combining the plots of FIGS. 2 and 3;

FIG. 5 are plots of refractive index (RI) and light scattering (LS) signal intensities (mV) vs. time (minutes) for two 300 mg aliquots of insulin;

FIG. 6 are plots of refractive index (RI) and light scattering (LS) signal intensities (mV) vs. time (minutes) for three 300 mg samples of polyvinylphosphonic acid;

FIG. 7 are plots of refractive index (RI) and light scattering (LS) signal intensities (mV) vs. time (minutes) for the addition of polyvinylphosphonic acid to insulin;

FIG. 8 are plots of turbidity (NTU) vs. time (min) for solutions of growth hormone having heparinic acid added thereto showing the effect of pH on the formation of a growth hormone-heparin complex;

FIGS. 9 and 10 are plots of % normal blood glucose vs. time for male rabbits administered either uncomplexed insulin or a macromolecular drug complex containing insulin and polyvinylphosphonic acid;

FIG. 11 are plots of % normal blood glucose vs. time for male rabbits administered either uncomplexed insulin or a macromolecular drug complex containing insulin and polyacrylic acid; and

FIG. 12 are plots of serum glucose concentration vs. time (minutes) after administration of a growth hormone complex showing the effect of GH on basal glucose levels in New Zealand white rabbits.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

It is well known that a wide range of biological functions are mediated by the formation of noncovalent, macromolecular complexes. Examples include enzyme-substrate binding, antigen-antibody interactions, leukocyte-endothelial cell adhesion events, drug-receptor binding, and protein-protein interactions. However, utilization of these self-assembling, ionic complexes as drug delivery systems is relatively new, and incorporation of such a complex into a microemulsion is uninvestigated. The physiochemical properties of one such macromolecular complex, prepared from human growth hormone and heparin, its formulation as a microemulsion, and absorption following parenteral administration to rabbits were investigated.

In particular, the present application discloses a drug delivery system which utilizes a macromolecular drug complex containing a drug and a naturally occurring or synthetic polymer, wherein the drug complex is incorporated into a microemulsion. The microemulsion containing the macromolecular drug complex is useful for the oral, parenteral, buccal, sublingual, transdermal, conjunctival, intraocular, intranasal, aural, intrarespiratory, rectal, vaginal, or urethral delivery of therapeutic agents. The therapeutic agent can be, for example, but not limited to, peptides, proteins, antibacterials, antifungals, antineoplastics, antiprotozoals, antiarthritics, and antiinflammatory agents. In a preferred embodiment, the therapeutic agent is a polypeptide or a protein. In especially preferred embodiments, the therapeutic agent is human growth hormone or insulin.

The physicochemical properties of the macromolecular drug complexes are disclosed in WO 97/37680, incorporated herein by reference. In particular, the interaction of insulin with various polymers was studied, and the formation of the macromolecular insulin complexes was confirmed. Turbidimetric analysis of an aqueous suspension of the complexes indicated that the physicochemical properties of the complexes vary with the initial complexing conditions. Preliminary solubility studies showed that the macromolecular drug complexes are well suited for delivery of therapeutic agents.

The following discussion is particularly directed to the preparation, characterization, and evaluation of water-in-oil microemulsions containing macromolecular drug complexes including human growth hormone (as the therapeutic agent) and heparin (as the polymer). The present drug delivery system comprises a macromolecular drug complex prepared from a mixture of a therapeutic agent and a natural or synthetic anionic polymer. Once formed, the complex is incorporated into the dispersed phase or continuous phase of an oil-in-water (O/W) or water-in-oil (W/O) microemulsion, respectively. The microemulsions containing the macromolecular drug complex then can be administered by a variety of routes, including oral and parenteral.

Complexation of human growth hormone (GH), a 20 kD (kilodalton) protein, with heparin, which is an endogenous anionic polysaccharide, was confirmed visually and by turbidimetry. In particular, visually clear, aqueous solutions of growth hormone and heparinic acid were mixed at specific weight ratios. The immediate formation of an opalescent colloidal solution indicated the formation of the growth hormone heparin complex. Turbidimetric analysis of the resulting colloidal solution indicated that the pH of the complexing medium strongly influences the particle size and composition of the complex. Formulation of the GH-heparin complex into a water-in-oil microemulsion, and subsequent parenteral administration to rabbits indicated enhanced GH absorption.

Persons skilled in the art are aware that other drugs having the structural characteristics of human growth hormone, especially insulin and other polypeptide and protein therapeutic agents, similarly can be complexed with a polymer having a plurality of acid moieties to provide a macromolecular drug complex which then is incorporated into a microemulsion.

As previously discussed, a drug, like insulin, can treat and control a disease, like diabetes, but cannot prevent, attenuate, or rectify complications associated with the disease, such as vascular problems, like heart disease and “diabetic foot.” Therefore, it would be advantageous to administer a therapeutic agent to an individual in a form that not only treats the disease, but also prevents, alleviates, or reverses complications associated with the disease.

An additional advantage of the present invention is to provide human growth hormone in a form capable of treating diseases and conditions such as dwarfism, hypopituitarism, hypercholesterolemia, hypertension, depression, muscle wasting, osteoporosis, insomnia, menopause, impotence, as well as other conditions commonly associated with aging. The effect of human growth hormone in treating these diseases and conditions is set forth in the following table:

Condition Action of Growth Hormone Dwarfism stimulates osteoblast production Muscle wasting (AIDS) enhances lean muscle mass and reduces body fat through improved protein synthesis Hypercholesterolemia reduces cholesterol (lowers LDL) Osteoporosis enhances bone density through the stimulation of osteoblast growth Autoimmune disorders enhances immune system efficiency Condition Action of Growth Hormone Hypertension assists in the regulation of blood pressure Depression alleviates the symptoms and syndromes associated with depression through its mood-elevating characteristics and by its effect on other hormones such as thyroid-stimulating hormone (TSH), melatonin, DHEA, IGF-1, and testosterone. Impotence enhances blood flow and improves hor- monal functioning and utilization Aging enhances speed and efficiency of wound healing Aging enhances skin elasticity and thick- ness Aging facilitates hair regrowth and hair color restoration in some individuals

The macromolecular drug complex and drug delivery system of the present invention provide improved treatment of such diseases and conditions by increasing the amount of human growth hormone delivered to cells. A microemulsion containing a macromolecular growth hormone complex delivers more growth hormone to the cells than growth hormone injections because of enhanced bioavailability. The macromolecular growth hormone complex also can treat the syndromes associated with vascular degeneration, including cardiovascular disease, kidney disease, as well as thrombotic conditions, which cannot be treated by conventional growth hormone formulations or delivery systems.

An important additional advantage would be to provide a method of administering a drug, like insulin, human growth hormone, and many other protein and polypeptide-based drugs, orally. Such drugs, cannot be administered orally because the drug is altered in the stomach, and, therefore, is unavailable to the body in a form to combat or control a disease.

With respect to diabetes, it is known that glucose can complex with proteins to produce toxic by-products. Such toxic by-products have been theorized as the cause of the complications associated with diabetes. It also has been observed that diabetics have elevated levels of GAGs in serum and urine, and a lower GAG content in their kidney cell membranes. It also is known that administration of GAGs to diabetic animals inhibited and/or reversed some vascular abnormalities associated with diabetes. Diabetics also have altered blood chemistries, including elevated levels of various enzymes in addition to glucose.

Therefore, the following has been hypothesized, but is not relied upon, as a cause for the complications associated with diabetes, and possibly other diseases. In particular, the interior of vascular walls are lined with endothelial cells. Branching from the endothelial cells are proteoglycan molecules. Glucose is able to bond with these surfaces of the endothelial cells. However, GAGs also are known to be present on the proteoglycan branches on the surface of endothelial cells. In addition, insulin and other therapeutic agents also are known to have the capability to complex with the GAG compounds. It is hypothesized, therefore, that insulin and other therapeutic agents complex with the GAGs present on the branches of the endothelial cells, and that the GAGs-drug complexes are removed from the cell by enzymatic activity, thereby leaving the surfaces endothelial cells devoid of GAGs compounds.

An increased drug dosage provides sufficient drug to account for the drug lost as a result of the insulin-GAGs interaction. But the sloughing of GAGs from endothelial cells exposes the vascular surface to numerous unwanted reactions, including repeated glycosylation. In addition, repeated glycosylation can be exacerbated by the naturally elevated levels of serum glucose in a diabetic. It has been found that the interaction between a therapeutic agent and the GAGs on the endothelial cells can be circumvented by complexing insulin, and other therapeutic agents, such that the therapeutic agent is unavailable to interact with the GAGs on the surface of endothelial cells.

Evidence exists that a GAGs complex forms with insulin. It therefore was suggested to complex insulin with a GAG, and thereby protect vascular endothelial cells from the harmful effects of constant exposure to insulin, for example. Then, the insulin would not be available to complex with GAGs on the surface of endothelial cells. As a result, the endothelial cells would not be vulnerable to glycosylation as a result of a sloughing off of the GAGs-insulin complex.

However, high molecular weight GAGs are well known anticoagulants and their long term effects on a diabetic are unknown. As a result, a GAG could not be administered to an individual on a long term basis because, for example, the blood of the individuals would be thinned too greatly.

In accordance with the present invention, it has been shown that human growth hormone, insulin, and other drugs, can be complexed with naturally occurring and synthetic polymers, to provide a macromolecular drug complex that avoids the interaction between the therapeutic agent and a GAG on the surface of an endothelial cell. It is hypothesized that the vascular endothelial cells, therefore, are spared from undesirable reactions, like glycosylation, and vascular complications associated with the disease or condition being treated can be eliminated or attenuated. Furthermore, the present macromolecular drug complexes make the therapeutic agent available to the individual, such that the disease or condition is controlled. However, other drugs, in addition to human growth hormone and insulin, can be complexed, and are available to treat the disease or condition of concern.

The use of a suitable naturally occurring or synthetic polymer also avoids the harmful side effects of GAGs (e.g., anticoagulation), and insures the quality, reproducibility, and uniformity of the macromolecular drug complex because the polymers have a reproducible chemical makeup, and the molecular weight can be controlled. Furthermore, by a proper selection of a polymer, the in vivo behavior of the therapeutic agent can be controlled to optimize the pharmacologic response of the therapeutic agent, and the route of administration can be regulated.

The therapeutic agent present in the macromolecular drug complex can be any drug capable of complexing with an acid moiety. Typically, the drug has at least one positively charged site. The positively charged site usually is a quaternary ammonium nitrogen atom. The drug can be a naturally occurring or synthetic drug. The drug can be monomeric, or oligomeric or polymeric, like a polypeptide or protein. Preferred drugs are polypeptide or protein based.

If the drug is a synthetic drug, the drug often contains a nitrogen atom that can be quaternized. If the drug is a naturally occurring drug, the drug often contains an amino acid having a positively charged site. These quaternized nitrogen atoms and positively charged sites are available to complex with the acid moieties of the polymer.

For example, if the drug is insulin, insulin contains fifty-one amino acids in two polypeptide chains. The insulin molecule contains the amino acids lysine, arginine, and histidine. Each of these amino acids has a positively charged site, thereby permitting insulin to complex with the polymer through the acid moieties of the polymer. Similarly, human growth hormone contains 191 amino acids in two polypeptide chains. Human growth hormone also contains the amino acids lysine, arginine, and histidine, which, like insulin, contain positively charged sites thereby permitting the growth hormone to complex with the polymer through the acid moieties of the polymer. It should be understood that derivatives of human growth hormone containing 190 or 192 amino acids, and hydrolysis products of human growth hormone that behave identically or similarly to human growth hormone, are encompassed by the term “human growth hormone” as used herein.

Other drugs that can be complexed with a polymer having a plurality of acid moieties to form a macromolecular drug complex of the present invention include, but are not limited to, anti-inflammatory drugs, like tereofenamate, proglumetacin, tiaramide, apazone, benzpiperylon, pipebuzone, ramifenazone, and methotrexate; anti-infective drugs, like isoniazid, polymyxin, bacitracin, tuberactionomycin, and ethryomycin; antiarthritis drugs, like penicillamine, chloroquine phosphate, glucosamine, and hydroxychloroquine; diabetes drugs, like insulin, and glucagon; and anticancer drugs, like cyclophosphamide, interferon α, interferon β, interferon γ, vincristine, and vinblastine.

The polymer used to prepare the macromolecular drug complex has a plurality of acid moieties. Any physiologically acceptable polymer can be used as long as the polymer contains sufficient acid moieties to complex with the drug. Typically, the polymer has sufficient acid moieties if the polymer can be solubilized in water by neutralizing the polymer with a base. Such polymers are prepared from a monomer, or mixture of monomers, wherein at least 25% of the monomers, by weight of the polymer, contain an acid moiety. Preferably, at least 40% of the monomers, by weight of the polymer, contain an acid moiety. To achieve the full advantage of the present invention, at least 60% of the monomers, by weight of the polymer, contain an acid moiety. If the polymer is a homopolymer, the monomers containing an acid moiety can be 100% by weight of the polymer. By proper selection of the polymer, persons skilled in the art are able to regulate the pharmacologic response of the drug and the route of administration of the drug.

The polymer can be a synthetic polymer or a naturally occurring polymer. In general, the polymer has an M_(w) of about 1,000 to about 50,000, and preferably about 2,000 to about 20,000. To achieve the full advantage of the present invention, the polymer has an M_(w) of about 4,000 to about 15,000.

With respect to synthetic polymers, preferred polymers are linear polymers. However, lightly crosslinked polymers also can be used. A lightly crosslinked polymer has one to about five crosslinks crosslinking the linear chains of the polymer molecule and is soluble in water. An important feature of the polymer is that the polymer is water soluble or water dispersible, and contains acid moieties, such as carboxyl, phosphate, phosphonate, sulfate, sulfonate, phenolic, or any other moiety having a labile hydrogen that can be removed from the moiety to provide a negatively charged site on the polymer.

The polymer typically is an acrylic polymer containing a sufficient amount of acid-containing monomers, like acrylic acid, methacrylic acid, or vinylphosphonic acid. The acid-containing monomer can be, but is not limited to, acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, mesaconic acid, citraconic acid, vinylphosphonic acid, and similar α, β-unsaturated carboxylic acids and α, β-unsaturated dicarboxylic acids.

The polymer can be a homopolymer of an acid-containing monomers, like α, β-unsaturated carboxylic acids, or can be a copolymer. For example, a suitable copolymer can be an acid-containing monomer that is copolymerized with ethylene, propylene, or a similar C₄-C₅ alkene, or a C₁-C₁₂ ester of an α, β-unsaturated carboxylic acid, vinyl propionate, acrylamide, or methacrylamide, or that is co-polymerized with an aromatic monomer, like styrene, α-methyl toluene, or vinyl toluene. Other comonomers include vinylpyrrolidone, vinyl alcohol, vinyl acetate, and vinyl alkyl ethers.

Examples of polymers include, but are not limited to, polyacrylic acid, polyvinylphosphonic acid, polyvinylsulfonic acid, polystyrenesulfonic acid, polymaleic acid, polymethacrylic acid, polyvinylsulfuric acid, poly(2-methacroyloxyethane-1-sulfonic acid, poly(4-vinylbenzoic acid), poly(3-(vinyloxy)propane-1-sulfonic acid), poly(3-(vinyloxy)propane-1-sulfonic acid), poly(3-methacryloxypropane-1-sulfonic acid), polymethacrylic acid, poly(4-vinylphenol), poly(4-vinylphenyl sulfuric acid), and poly(N-vinylsuccinamidic acid). In other embodiments, a polymer containing an aromatic monomer can be sulfonated or sulfated to position acid groups on the aromatic monomer. Preferred polymers are polyacrylic acid and polyvinylphosphonic acid.

With respect to naturally occurring polymers, the above-discussed disadvantages resulting from using a GAG limits the naturally occurring polymers to those that do not adversely effect an individual over the long term, i.e., a strong anticoagulant should not be used as the polymer. However, GAGs that act as anticoagulants have a relatively high molecular weight of about 12,000 or greater. Therefore, analogs of GAGs that do not act as strong anticoagulants can be used as the polymer. Such polymers have a structure that is similar to a GAG compound, but have a lower M_(w), i.e., less than about 12,000.

Therefore, useful naturally occurring polymers have an M_(w) of about 1,000 to about 12,000, and preferably about 2,000 to about 8,000, and do not act as coagulants at the level they are administered in the macromolecular drug complex, i.e., about 2 mg/day. This dose is less than the 20 mg/day dose required to observe anticoagulation effects and, therefore, mild anticoagulants can be used as the polymer. Furthermore, the low M_(w), naturally occurring polymers have a greater bioavailability. For example, heparin having an M_(w) of about 6,000 is 85% bioavailable, but as the M_(w) increases, bioavailability decreases exponentially. Suitable naturally occurring polymers, therefore, include, but are not limited to, heparin, dermatan sulfate, chondroitin sulfate, keratan sulfate, heparin sulfate, hyaluronic acid, the various forms of carrageenan, and mixtures thereof, having a molecular weight (M_(w)) of about 1,000 to about 12,000. Overall, a synthetic polymer is preferred over a naturally occurring polymer because synthetic polymers are more uniform chemically, and a desired M_(w) is more easily achieved.

To illustrate the ability of a drug to form a macromolecular drug complex with a polymer having a plurality of acid moieties, an aqueous insulin solution was admixed with an aqueous solution of polyvinylphosphonic acid. In this experiment, a stock solution of insulin, available from Sigma Chemical Co., St. Louis, Mo., was prepared at a known concentration and varying amounts polyvinylphosphonic acid, available from Polysciences, Inc., Warrington, Pa., were added to the insulin. Macromolecular insulin complex formation was detected visually by the appearance of a white, fluffy precipitate and quantified by turbidimetric measurements.

In addition to insulin, macromolecular drug complexes were prepared in an identical manner using the drugs methotrexate, isoniazid, and chloroquine phosphate. Other macromolecular drug complexes were prepared using polyacrylic acid as the polymer.

FIG. 2 shows the effect of polymer addition to a solution containing 1.0 mg/mL insulin on the turbidity of the resulting mixture. An increase in the turbidity of the mixture as polymer is added to an insulin solutions shows complex formation. FIG. 2 shows formation of the complex (i.e., the solution becomes turbid) with the addition of 22% polymer, by weight of polymer and insulin.

However, when the polymer concentration is fixed at 1.0 mg/mL, and varying amounts of insulin are combined with the polymer, different results are observed, as illustrated in FIG. 3. In FIG. 3, an increase in turbidity again is indicative of complex formation. The plots of FIG. 3 show that complex formation was detected at low levels of polymer, but higher polymer concentrations produced a clear solution. The plots in FIGS. 2 and 3 show that complex formation is dependent upon several factors, including the order of addition of the drug and polymer and the weight ratio of the drug to the polymer. FIG. 4 combines the plots of FIGS. 2 and 3 to more clearly show the variables with respect to forming a macromolecular drug complex.

In particular, further tests showed that complex formation is optimized by adding the polymer to the drug, and by using minimal agitation or stirring to mix the reactants. Good complex formation however was observed when the drug was added to the polymer with minimal or no agitation or stirring.

To confirm formation of a macromolecular drug complex, a technique to determine the molecular weight of polymers in solution, termed continuous-flow multi-angle laser-light scattering (CF-MALLS), was developed. The CF-MALLS technique makes a molecular weight determination quickly without using chromatography and with little or no sample preparation. In particular, a refractive index (RI) detector (Waters 410, Waters Corp, Cambridge, Mass.) was connected in series to a light scattering (LS) detector (MiniDawn Multi-Angle Laser Light Scattering Detector, Wyatt Technologies, Santa Barbara, Calif.) and a continuous flow multistatic pump. Simply continuously circulating a solution through the detectors permits measurement of the polymer molecular weight in solution.

The CF-MALLS technique was performed on polymers of known molecular weight, and provided excellent correlation between experimental results and known molecular weights. The results are summarized in Table 1 below.

TABLE 1 MOLECULAR WEIGHT ANALYSIS OF POLYMER STANDARDS AND INSULIN/POLYMER COMPLEXES BY CONTINUOUS-FLOW MULTI-ANGLE LASER-LIGHT SCATTERING AND BY GAS PHASE CHROMATOGRAPHY (GPC) M_(w) (g/mol) M_(w) (g/mol) POLYMER (GPC) (CF-MALLS) Pullulan Standard 12,200 12,232 ± 300 Dextran 36,000 34,680 ± 200 Bovine Serum Albumin 66,450 67,854 ± 400 Dextran 72,000 69,970 ± 300 Pullulan Standard 380,000  285,525 ± 250  Insulin  6,000  9,045 ± 200 PVPA¹⁾  5,000 4,051 ± 30 PVPA/Insulin    30,470-59,460²⁾ (30:70 by weight) PVPA/Insulin  162,100-218,100 (50:50 by weight) PVPA/Insulin   40,010-371,400 (90:10 by weight) ¹⁾PVPA is Polyvinylphosponic acid; ²⁾The first value represents the M_(w) of the complex immediately after admixing the insulin polymer, the second value represents the M_(w) at a later time, i.e., real-time complex formation.

The CF-MALLS technique also illustrates formation of the macromolecular drug complex over time. FIG. 5 shows an analysis of insulin using the CF-MALLS technique. Adding insulin to an aqueous medium, in 300 mg aliquots, at time zero and again about 87 minutes, shows that the RI and LS detectors yield equivalent signal intensities for each addition of insulin, i.e., the detectors merely detected an increase in the concentration of insulin, not an increase in M_(w). The M_(w) values were calculated from Rayleigh's equation after each insulin addition. The M_(w) values were about 9,000 g/mol and about 10,540 g/mol. The known M_(w) of insulin is about 6,000 g/mol. The increased M_(w) is attributed to physical entanglements of insulin molecules, which, as expected, increase as the insulin concentration in increases.

FIG. 6 shows a similar analysis for polyvinylphosphonic acid after three separate additions of 300 mg of polyvinylphosphonic acid to an aqueous medium at time zero, at about 60 minutes, and at about 100 minutes. Like insulin, the RI and LS detectors show equivalent signal intensities for each addition of polyvinylphosphonic acid, i.e., the detectors detected an increase in the concentration of polyvinylphosphonic acid. The test also allowed determination of the M_(w) of polyvinylphosphonic acid after each addition, i.e., 8,260, 9,206, and 9,459 g/mol, respectively. The M_(w) of pure polyvinylphosphonic acid is 4,051 g/mol. However, like insulin, the apparent M_(w) of polyvinylphosphonic acid is greater in aqueous solution because of dimerization, and physical interactions, like chain entanglements, which increase with increasing polymer concentration. The M_(w) again was calculated using Rayleigh's equation after each polymer addition.

FIG. 7 shows complex formation between insulin and polyvinylphosphonic acid. In this test, insulin (300 mg aliquots) were added to an aqueous medium at time zero and after 87 minutes. The results were identical to the results in FIG. 5. However, a subsequent addition of two 300 mg portions of polyvinylphosphonic acid to the resulting insulin solution at 160 minutes and 240 minutes produced a lower increase in RI than expected from FIG. 6, and a disproportionately greater increase in the LS signal than expected from FIG. 6.

Although the molecular weight of pure polyvinylphosphonic acid is 4051 g/mol, the M_(w) of the resulting macromolecular drug complex increased to 33,030 g/mol at 220 minutes. The subsequent addition of an additional 300 mg of polyvinylphosphonic acid resulted in a macromolecular drug complex having an initial M_(w) of 162,100 g/mol, which rapidly increased to 236,600 g/mol at 265 minutes. Accordingly, the large increase in M_(w) after the first addition of polyvinylphosphonic acid, and the exponential increase in M_(w) after the second addition of polyvinylphosphonic acid, demonstrated that a macromolecular drug complex was formed.

Tests also were performed to illustrate that other proteins, like human growth hormone, form noncovalent macromolecular complexes with naturally occurring polymers, like heparin, for example. In particular, a stock aqueous solution of growth hormone, available from Sigma Chemical Co., St. Louis, Mo., containing about 1.0 mg hormone/mL solution, was prepared by suspending a weighed amount of the GH in a known volume of water with gentle, constant stirring. Complete solubilization of the GH was achieved by titrating the suspension with 0.10 N sodium hydroxide (NaOH) until a visually clear solution was obtained. Separately, heparinic acid was prepared by passing an aqueous solution of heparin sodium salt through the acidic form (H⁺) of a cation exchange resin.

The growth hormone solution was divided into two equal aliquots and the pH of one aliquot adjusted to 8.5 with 0.10 N NaOH. In separate experiments, each aliquot of GH was placed in the sample cuvette of a Monitek Model TA21 nephelometer, available from Monitek Technologies, Hayward, Calif., and the turbidity of the solution was monitored continuously upon the addition heparinic acid. In particular, in two separate experiments, the nephelometer was charged with 17.0 mL of a 1.058 mg/mL stock solution of growth hormone at a pH of 2.7 or 8.5. About 1.0 mL aliquots of heparinic acid were added at 12, 32, and 52 minutes for alkaline growth hormone, and an aliquot of heparinic acid at 11 minutes for acidic growth hormone.

FIG. 8 shows the effect of heparinic acid addition on the turbidity of the resulting solutions. An increase in turbidity after each addition is indicative of complex formation. The data summarized in FIG. 8 show that growth hormone and heparin form macromolecular complexes under acidic and basic conditions. Complexation is evidenced by an increase in turbidity. Furthermore, FIG. 8 shows that the degree of complexation, as evidenced by enhanced turbidity, is directly related to the pH of the medium, i.e., GH and heparin form larger complexes at lower pH values.

In addition to demonstrating that a noncovalent, i.e., ionic, macromolecular drug complex can be formed, it also was demonstrated that the complex has the ability to release the drug in vivo to treat a disease. In particular, a series of in vivo studies were performed to evaluate the effect of the macromolecular drug complex on serum glucose levels in normal, adult male, New Zealand white rabbits. In these studies, a rabbit, weighing three to five kilograms, was fasted overnight. Prior to dosing, the ears of the rabbit were shaved and anesthetized with a topical cream (i.e., Emla cream). A 22 gauge catheter was inserted into the left marginal ear vein, and a 0.50 mL blood sample withdrawn to establish basal serum glucose levels. A 0.050 units/Kg bolus dose of either insulin or a macromolecular insulin complex was injected into the right marginal ear vein, and 0.50 mL blood samples were withdrawn every 10 minutes for the first hour, every 20 minutes for the second hour, and every 30 minutes for the third hour post dosing. Serum glucose levels were determined utilizing standard glucose assays. Approximately 50 mL of blood was assayed immediately after sampling using a One Touch Glucometer, available from LifeScan, Inc., and the remainder of the sample was analyzed by a standard glucose colorimetric assay, available from Sigma Diagnostics, as Assay #DA510. The results are illustrated in FIGS. 9 and 10.

As illustrated in FIG. 9, uncomplexed insulin was compared to macromolecular insulin complexes at an insulin dose of 0.050 units/Kg. The macromolecular insulin complexes containing 90% polymer and 10% insulin (90:10, wt/wt) were prepared by mixing aqueous solutions of insulin and polyvinylphosphonic acid (i.e., native insulin), or by mixing the compounds and then subjecting the complex to low levels of shear (i.e., processed insulin). Similar native and processed complexes containing 50:50 wt/wt insulin and polymer also were prepared. The complexes were administered to fasted, adult male rats, and serum glucose levels were assayed periodically.

The macromolecular drug complexes, as shown in FIGS. 9-11, are capable of reducing serum glucose levels, but not as greatly as uncomplexed insulin. The macromolecular complexes containing processed insulin, as shown in FIG. 9, which were subjected to low levels of shear, reduced the serum glucose levels to a lesser extent than macromolecular complexes containing native insulin. The reduction in glucose levels achieved by uncomplexed insulin, however, can be attained by simply increasing the dose of the macromolecular insulin complex. Such dosage adjustments are well known and long practiced in the treatment of diabetics.

The results in FIGS. 9 and 10 show that the macromolecular complexes remain intact and do not dissociate immediately after intravenous administration. It also has been shown that the efficacy of insulin can be altered by formulating insulin as a macromolecular complex with polyvinylphosphonic acid. Furthermore, FIGS. 9 and 10 show that a 50:50 insulin-polymer weight ratio reduced blood glucose more effectively than a 90:10 and a 10:90 insulin-polymer weight ratio.

FIG. 11 shows that a macromolecular drug complex containing insulin and polyacrylic acid (PAA) likewise reduces blood glucose levels in vivo. Therefore, polyacrylic acid also can be used as the polymer to prepare a macromolecular drug complex, and to effectively deliver insulin.

During these tests different weight ratios of insulin to polyvinylphosphonic acid were used to prepare the macromolecular drug complexes. In particular, various macromolecular drug complexes were prepared, then centrifuged, and the supernatant liquid was analyzed for the presence of insulin and polyvinylphosphonic acid. The results are summarized in Table 2. The data in Table 2 shows that to achieve optimum complexing the weight ratio of polymer (P) to insulin (I) is at least about 10:90 by weight. The ratio of P to I can be as high as about 90:10. A preferred weight ratio of P to I is about 10:90 to about 75:25. To achieve the full advantage of the present invention, the P to I ratio is about 12.5: 87.5 to about 25:75 because, as shown in Table 2, the amount of insulin and polyvinylphosphonic acid in the supernatant liquid was negligible. Accordingly, essentially all of the insulin and polyvinylphosphonic acid were complexed in the macromolecular drug complex.

TABLE 2 % EXCESS POLYVINYLPHOSPHONIC ACID (PVPA) AND INSULIN IN SUPERNATANT USING VARIOUS WEIGHT RATIOS OF PVPA AND INSULIN % free PVPA in % free Insulin Weight Ratio of P:I supernatant in supernatant  5:95 0.16 65 10:90 0.11 9.2 12.5:87.5 0.21 3.3 15:85 0.24 0 25:75 2 0 40:60 54.5 0 60:40 70.5 0

The solubility of the macromolecular polymer complex containing insulin also was measured under various conditions and compared to standard insulin. The results are summarized in Table 3.

TABLE 3 SOLUBILITY OF INSULIN AND MACROMOLECULAR INSULIN COMPLEX Macromolecular Insulin Insulin Complex pH = 3 Soluble Insoluble pH = 7 Insoluble Soluble pH = 7; Insoluble Soluble phosphate buffer

The data in Table 3 shows that the solubility of uncomplexed insulin compared to the macromolecular insulin complex is reversed when the pH is increased from 3 to 7. The macromolecular complex is insoluble at low pH, but is soluble at neutral pH. Furthermore, the macromolecular complex is soluble in neutral buffer, whereas uncomplexed insulin is not. These results indicate that the new macromolecular insulin complexes can be used in a composition suitable for the oral administration of insulin.

In particular, a water soluble macromolecular insulin complex can be formed by complexing insulin with a neutralized form of the polymer. The neutralized form of the polymer is prepared by adding a base to an aqueous solution the polymer. The base typically is an alkali metal hydroxide, like sodium hydroxide or potassium hydroxide. However, other physiologically acceptable alkalis can be used to neutralize the polymer. When using a neutralized form of the acid to form the macromolecular drug complex, the complex does not precipitate from solution after formation, but remains in solution.

A solid macromolecular complex is formed by complexing insulin with the free acid form of the polymer. In particular, an insulin solution is combined with an aqueous solution of the acid form of the polymer, and a precipitate forms. This precipitate, i.e., the macromolecular insulin complex, is insoluble in aqueous media at an acidic pH.

After formation of the macromolecular drug complex, the complex is isolated (if necessary), suspended in water, then incorporated into a microemulsion. The macromolecular drug complex is relatively hydrophobic, and, therefore, has a tendency to concentrate in the oil phase of the microemulsion, i.e., the dispersed phase of an oil-in-water emulsion or the continuous phase in a water-in-oil emulsion. The presence of the macromolecular drug complex in the oil phase has advantages, e.g., the therapeutic agent is less susceptible to hydrolysis and oxidation. As demonstrated hereafter, a microemulsion containing the macromolecular drug complex also delivers the drug more effectively.

The following test shows the effect of complexing GH on the hydrophilicity of GH. In this test, the partitioning of GH in water-octanol and in water-CAPTEX 355 systems were estimated. CAPTEX 355 is a mixture of C₈/C₁₀ triglycerides, and is available from Abitec Corp., Columbus, Ohio. As discussed hereafter, CAPTEX 355 is a common microemulsion ingredient used as the oil phase. Known amounts of GH and a GH-heparin complex were allowed to partition between equal volumes of water and 1-octanol, and between equal volumes of water and CAPTEX 355. After equilibration, the aqueous phase from each partitioning system was isolated, and the amount of growth hormone present in the water was determined by a modified Micro Lowry method (Sigma Diagnostics Kit #690A, St. Louis, Mo). The results are summarized in Table 4.

TABLE 4 Weight % of Growth Hormone Remaining in Aqueous Phase After Oil/Water Partitioning Growth Hormone Growth Hormone- Partitioning System (uncomplexed) Heparin Complex Octanol/water 73.7% 43.9% CAPTEX 355/water 73.6% 34.3%

The results in Table 4 show that the amount of GH remaining in the aqueous phase decreased by about 50% after complexation with heparin, and the amount of GH partitioning into the oil phase significantly increased. These results show that the GH-polymer complex is more lipophilic (i.e., more hydrophobic) than uncomplexed GH. Because lipophilic drugs typically are absorbed to a greater extent than hydrophilic drugs, the GH-heparin complex is expected to demonstrate enhanced absorption in vivo compared to uncomplexed GH.

The identity of the components utilized to prepare the microemulsion is not limited, as long as a component does not adversely effect the macromolecular drug complex, either by chemically interacting with the complex or by hindering release of the therapeutic agent from the macromolecular drug complex. Microemulsions, their preparation, and components used to form the microemulsion are well known to persons skilled in the art.

In general, a microemulsion is a thermodynamically stable, liquid solution that contains water, oil (or other nonpolar compounds), and at least one amphiphile. Many microemulsions also contain one or more inorganic salts. The oil and the amphiphile components can be single components, or the oil, the amphiphile, or both can be a mixture of compounds. Many microemulsions contain both a surfactant as the amphiphile, and a cosurfactant or cosolvent, i.e., an amphiphile having a molecular weight that is too low to be a true surfactant.

Microemulsions are stable dispersions of one liquid in another, in the form of spherical droplets having a diameter that is less than one-quarter the wavelength of white liquid. Therefore, light can pass through a microemulsion, and the microemulsion appears to be transparent. Microemulsions are discussed generally, for example, in Kirk-Othmer Encyclopedia of Chemical Technology, 4th Ed. (Supplement), pages 299-314 (1998).

An example of a useful microemulsion useful in the present invention is disclosed in P. P. Constantinides et al., Pharm. Res., 11(10), pages 1385-1390 (1994). Constantinides et al. disclose a self-emulsifying water-in-oil microemulsion containing CAPTEX 355 as the oil, and CAPMUL MCM and TWEEN 80 as the amphiphiles. CAPTEX 355 contains C₈/C₁₀ triglycerides having a fatty acid distribution of 55% caprylic acid (C₈), 42% capric acid (C₁₀), and 2% caproic acid (C₆). CAPMUL MCM is a 1:1 mixture of C₈/C₁₀ mono-/diglycerides having a fatty acid distribution of 55% caprylic acid (C₈), 30% capric acid (C₁₀), 3.2% caproic acid (C₆), less than 1% palmitic acid (C₁₆), and 2% free glycerol. CAPTEX 355 and CAPMUL MCM are available from Abitec Corporation, Columbus, Ohio. TWEEN 80 is polyoxyethylene (20) sorbitan monooleate, available from numerous commercial sources, like Sigma Chemical Co., St. Louis, Mo.

Microemulsions based on the Constantinides et al. disclosure were prepared, and the macromolecular GH-heparin complex was incorporated into the microemulsions. In particular, the GH-heparin complex was incorporated into oil-in-water microemulsions containing a medium-chain fatty acid triglyceride (CAPMUL MCM); an oil (CAPTEX 355); TWEEN 80; and water. The visually clear, isotropic water-in-oil microemulsions were formed at specific weight ratios of these components. The approximate weight ratio of each component at the extremes of the entire microemulsion region are summarized in Table 5.

TABLE 5 Weight % Range for Microemulsion Microemulsion Formation Component Highest % of Oil Highest % of Water CAPTEX 355 64 7.2 CAPMUL MCM 21 2.5 TWEEN 80 10 55 Water  5 35

Such microemulsions were prepared and utilized as a delivery system for macromolecular drug complexes comprising a therapeutic agent and a polymer.

To illustrate the drug delivery ability of a microemulsion containing a macromolecular GH-heparin complex, GH formulations were administered, in vivo, intravenously and intratracheally. A recent review of the in vivo behavior of growth hormone and assays for monitoring the effect of GH therapy discloses that GH treatment produces an acute hypoglycemic response in humans (H. Guyda, Horm. Res., 48 (Suppl. 5), pages 1-10 (1997)). Although serum glucose levels do not predict the outcome of GH therapy, monitoring serum glucose levels can be used to evaluate the degree of GH absorption from various formulations. Therefore, a number of tests were conducted to determine if serum glucose levels decreased following parenteral administration of various GH formulations.

Male, New Zealand white rabbits, each approximately 3-4 kilograms in weight, were fasted (water only) overnight. Each rabbit received one of the following GH formulations: (1) 1.8 μg/kg GH-heparin complex intravenously (IV), (2) 1.8 μg/kg GH solution intravenously, (3) 36 μg/kg GH-heparin complex solution, via intratracheal administration (IT), or (4) 36 μg/kg GH-heparin complex microemulsion, via intratracheal administration. Approximately 0.50 mL of blood was collected periodically from the marginal ear vein, and glucose levels determined using a One Touch™ Basic Glucometer. The results are summarized in FIG. 12.

As illustrated in FIG. 12, serum glucose levels decreased following intravenous (IV) administration of a GH solution alone or a macromolecular GH-heparin complex formulated in a microemulsion. Serum glucose levels showed a similar hypoglycemic response following intratracheal (IT) administration of the GH-heparin macromolecular complex and following the administration of the GH-heparin microemulsion. The results in FIG. 12 show that GH is absorbed following intratracheal administration of GH-heparin complex or the GH-heparin microemulsion. In addition, administration of a microemulsion containing the macromolecular GH-heparin complex has the advantage of lessening the acute hypoglycemic effect that is associated with GH therapy. FIG. 12 also shows a delayed hypoglycemic effect by the microemulsion and macromolecular drug complex compared to a GH solution. This delayed effect illustrates the time release of the GH from the microemulsion and macromolecular drug complex.

The present invention, therefore, discloses a novel drug delivery system for the oral, parenteral, sublingual, transdermal, conjunctival, intraocular, intranasal, aural, intrarespiratory, rectal, vaginal, or urethral delivery of therapeutic agents. The drug delivery system is a microemulsion composition comprising a macromolecular drug complex containing a polymer having a plurality of acid moieties and a therapeutic agent, including, but not limited to peptides, proteins, antibacterials, antifungals, antineoplastics, antiprotozoals, antiarthritics, and anti-inflammatory agents. The polymers can be naturally occurring or synthetic, and are commercially available or can be readily synthesized.

The macromolecular drug complexes are either entrapped in the dispersed phase or distributed in the continuous phase of oil-in-water (O/W) or water-in-oil (W/O) microemulsion, respectively. The microemulsion formulations then can be administered by a variety of oral and parenteral routes.

In addition, although the present disclosure is particularly directed to the preparation of a macromolecular insulin and growth hormone complexes, persons skilled in the art can apply this technology to a variety of therapeutic agents capable of complexing with a polymer having a plurality of acid moieties. The complexes are prepared by simply admixing the polymer, either in the free acid or neutralized form, with the therapeutic agent in an aqueous medium. The specific physicochemical properties of the resulting macromolecular complex can be adjusted by a judicious selection of the polymer and the M_(w) of the polymer, by the number and type of acid moieties on the polymer, by the weight ratio of drug to polymer in the macromolecular complex, and by the number and type of polymer crosslinks.

Furthermore, although the present disclosure describes the preparation, characterization, and evaluation of a water-in-oil microemulsion containing a macromolecular complex prepared from growth hormone (GH) and heparin, persons skilled in the art can apply this technology to other microemulsions for administration of the macromolecular drug complex.

Therefore, many modifications and variations of the invention as hereinbefore set forth can be made without departing from the spirit and scope thereof, and only such limitations should be imposed as are indicated by the appended claims. 

What is claimed is:
 1. A drug composition comprising (a) a macromolecular drug complex comprising (i) a drug having at least one quaternary ammonium nitrogen atom; and (ii) a polymer having a plurality of acid moieties and a weight average molecular weight of about 2,000 to about 12,000, wherein the acid moieties of the polymer are selected from the group consisting of carboxyl, phosphate, phosphonate, sulfate, sulfonate, phenolic, and mixtures thereof, for noncovalent complexing with the quaternary ammonium nitrogen atom of the drug, wherein the complex is water-insoluble at an acidic pH and has a weight ratio of the drug to the polymer in the complex of about 10:90 to about 90:10, and wherein the formation of the macromolecular drug complex is confirmed by the CF-MALLS technique, and (b) a microemulsion consisting essentially of (i) an oil; (ii) an amphiphile; and (iii) water.
 2. The composition of claim 1 wherein the drug is a polypeptide or a protein.
 3. The composition of claim 1 wherein the drug is selected from the group consisting of insulin, human growth hormone, tereofenamate, proglumetacin, tiaramide, apazone, benzpiperylon, pipebuzone, ramifenazone, methotrexate, isoniazid, polymyxin, bacitracin, tuberactionomycin, ethryomycin, penicillamine, chloroquine phosphate, glucosamine, hydroxychloroquine, glucagon, cyclophosphamide, interferon α, interferon β, interferon γ, vincristine, and vinblastine.
 4. The composition of claim 1 wherein the drug is selected from the group consisting of insulin, human growth hormone, methotrexate, polymyxin, bacitracin, tuberactionomycin, chloroquine phosphate, glucagon, interferon α, interferon β, and interferon γ.
 5. The composition of claim 1 wherein the drug is insulin.
 6. The composition of claim 1 wherein the drug is human growth hormone.
 7. The composition of claim 1 wherein the polymer comprises about 25% to 100%, by weight of the polymer, of a monomer having an acid moiety.
 8. The composition of claim 1 wherein the polymer is lightly crosslinked.
 9. The composition of claim 1 wherein the polymer is a synthetic polymer.
 10. The composition of claim 9 wherein the synthetic polymer is a homopolymer of an α,β-unsaturated carboxylic acid.
 11. The composition of claim 9 wherein the synthetic polymer is a copolymer of an α,β-unsaturated carboxylic acid and a comonomer.
 12. The composition of claim 11 wherein the comonomer is selected from the group consisting of ethylene, propylene, a C₄-C₅ alkene, a C₁-C₁₂ ester of an α,β-unsaturated carboxylic acid ester, vinyl propionate, acrylamide, methacrylamide, styrene, α-methyl toluene, vinyl toluene, vinylpyrrolidone, vinyl alcohol, vinyl acetate, a vinyl alkyl ether, and mixtures thereof.
 13. The composition of claim 10 wherein the α,β-unsaturated carboxylic acid is selected from the group consisting of acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, mesaconic acid, citraconic acid, vinylphosphonic acid, and mixtures thereof.
 14. The composition of claim 9 wherein the polymer comprises sulfated aromatic monomers or sulfonated aromatic monomers.
 15. The composition of claim 1 wherein the polymer is selected from the group consisting of polyacrylic acid, polyvinylphosphonic acid, polyvinylsulfonic acid, polystyrenesulfonic acid, polymaleic acid, polymethacrylic acid, polyvinylsulfuric acid, poly(2-methacroyloxyethane-1-sulfonic acid), poly(4-vinylbenzoic acid), poly(3-(vinyloxy)propane-1-sulfonic acid), poly(3-methacryloxypropane-1-sulfonic acid), polymethacrylic acid, poly(4-vinylphenol), poly(4-vinylphenyl sulfuric acid), poly(N-vinylsuccinamidic acid), and mixtures thereof.
 16. The composition of claim 1 wherein the polymer is selected from the group consisting of polyvinylphosphonic acid and polyacrylic acid.
 17. The composition of claim 1 wherein the weight ratio of the drug to the polymer is about 10:90 to about 75:25.
 18. The composition of claim 1 wherein the weight ratio of the drug to the polymer is about 12.5:87.5 to about 50:50.
 19. The composition of claim 1 wherein the polymer is in a free acid form.
 20. The composition of claim 1 wherein the polymer is in a salt form.
 21. The composition of claim 1 wherein the complex is water soluble at pH 7 or greater.
 22. The composition of claim 1 wherein the drug is insulin or human growth hormone, and the polymer is selected from the group consisting of polyacrylic acid, polyvinylphosphonic acid, and mixtures thereof.
 23. The composition of claim 22 wherein the polymer has a weight average molecular weight of about 4,000 to about 12,000.
 24. The composition of claim 1 wherein the microemulsion is a water-in-oil emulsion.
 25. The composition of claim 1 wherein the microemulsion is an oil-in-water emulsion. 